This allows for zero-configuration offloading to a childhurd.
* gnu/services/virtualization.scm (operating-system-with-offloading-account):
New procedure.
(<hurd-vm-configuration>)[offloading?]: New field.
(hurd-vm-disk-image): Define ‘transform’ and use it.
(hurd-vm-activation): Generate SSH key for user ‘offloading’ and add
authorize it via /etc/childhurd/etc/ssh/authorized_keys.d.
(hurd-vm-configuration-offloading-ssh-key)
(hurd-vm-guix-extension): New procedures.
(hurd-vm-service-type): Add GUIX-SERVICE-TYPE extension.
* gnu/tests/virtualization.scm (run-childhurd-test)[import-module?]: New
procedure.
[os]: Add (gnu build install) and its closure to #:import-modules.
[test]: Add “copy-on-write store” and “offloading” tests.
* doc/guix.texi (Virtualization Services): Document it.